graysclassics

Fiesta V, 1.4 16valve. Starts fine, idles ok for a little while, touch the throttle and idle goes to hell. Drives like absolute crap.
When engine warm drives normally. Low mileage car. Changed throttle pedal/TPS and throttle body with absolutely no difference. If you disconnect the battery for a bit it seems to help as if the problem is with the ECU itself which has been changed in the past as the coil pack blew and took the ECU with it. If it had a throttle cable it would be the idle control valve but with the fly by wire system I am now at my wits end.... no faults on diagnostics. Help
p.s. changed the coil pack again and the fuel pump just to eliminate the poor running as described by by daughter but since discovered only has the issue when cold.
I have checked other posts but cannot find the answer so apologies if this has been asked before. Thanks guys.